MCAT BIOCHEMISTRY REVIEW QUESTIONS 2024/2025 EXAM WITH 100% CORRECT ANSWERS.

MCAT BIOCHEMISTRY REVIEW QUESTIONS 2024/2025 EXAM
WITH 100% CORRECT ANSWERS



Amino Acid -- Correct Answer ✔✔ Dipolar compound containing an amino group and a
t t t t t t t t t t t t t t




carboxyl group t




Amino Group -- Correct Answer ✔✔ -NH2
t t t t t t




Carboxyl Group -- Correct Answer ✔✔ -COOH t t t t t t




Alpha Carbon -- Correct Answer ✔✔ Central carbon atom in amino acid
t t t t t t t t t t t




Attached to amino & carboxyl groups, H atom, and side chain
t t t t t t t t t t




Side Chain -- Correct Answer ✔✔ The variable component of an amino acid that gives the
t t t t t t t t t t t t t t t t




amino acid its identity and chemical properties
t t t t t t




also called R-group
t t




Chiral -- Correct Answer ✔✔ A molecule with a nonsuperimposable mirror image
t t t t t t t t t t t




All amino acids (except glycine) are chiral
t t t t t t




(S) Absolute Configuration -- Correct Answer ✔✔ All amino acids (except cysteine) have
t t t t t t t t t t t t t




an (S) absolute configuration
t t t




L-amino Acid -- Correct Answer ✔✔ All amino acids found in eukaryotes
t t t t t t t t t t t




Nonpolar, Nonaromatic Amino Acids -- Correct Answer ✔✔ Glycine, alanine, valine,
t t t t t t t t t t t




leucine, isoleucine, methionine, proline
t t t




Glycine -- Correct Answer ✔✔ Single H atom as side chain
t t t t t t t t t t




Achiral

,Smallest amino acid t t




Alanine -- Correct Answer ✔✔ Alkyl side chain (1C)
t t t t t t t t




Valine -- Correct Answer ✔✔ Alkyl side chain (3C)
t t t t t t t t




Leucine -- Correct Answer ✔✔ Alkyl side chain (4C)
t t t t t t t t




Isoleucine -- Correct Answer ✔✔ Alkyl side chain (4C)
t t t t t t t t




Methionine -- Correct Answer ✔✔ Methyl side chain (-CH3) t t t t t t t t




Contains S atom in side chain t t t t t




Proline -- Correct Answer ✔✔ Cyclic amino acid
t t t t t t t




N from amino group becomes part of side chain, forming five-part ring, limiting where is
t t t t t t t t t t t t t t t




can appear on a protein
t t t t




Rigid/constraints on flexibility t t




Aromatic Amino Acids -- Correct Answer ✔✔ Tryptophan, phenylalanine, tyrosine
t t t t t t t t t




Aromaticity -- Correct Answer ✔✔ The ability of a molecule to delocalize pi electrons
t t t t t t t t t t t t t t




around a conjucated ring, creating exceptional stability
t t t t t t




Tryptophan -- Correct Answer ✔✔ Double-ring system t t t t t t




Contains N atom in one ring t t t t t




Largest of aromatic amino acids
t t t t




Phenylalanine -- Correct Answer ✔✔ Benzyl side chain (benzene ring + -CH2 group)
t t t t t t t t t t t t




Smallest aromatic amino acid
t t t




Relatively nonpolar t




Tyrosine -- Correct Answer ✔✔ Phenylalanine + -OH group
t t t t t t t t




Relatively polar t

,Polar Amino Acids -- Correct Answer ✔✔ Serine, threonine, asparagine, glutamine,
t t t t t t t t t t t




cysteine

Polarity -- Correct Answer ✔✔ An uneven sharing of electrons in a molecule, creating a
t t t t t t t t t t t t t t t




slightly positive side and a slightly negative side
t t t t t t t




Serine -- Correct Answer ✔✔ -OH group in side chain
t t t t t t t t t




Highly polar - participate in H-bonding
t t t t t




Threonine -- Correct Answer ✔✔ -OH group in side chain
t t t t t t t t t




Highly polar - participate in H-bonding
t t t t t




Asparagine -- Correct Answer ✔✔ Amide (-NH2) side chain
t t t t t t t t




Amide N do not gain or lose protons with changes in pH - do not become charged
t t t t t t t t t t t t t t t t




Glutamine -- Correct Answer ✔✔ Amide (-NH2) side chain
t t t t t t t t




Amide N do not gain or lose protons with changes in pH - do not become charged
t t t t t t t t t t t t t t t t




Cysteine -- Correct Answer ✔✔ Thiol (-SH) side chain - weaker than OH bond
t t t t t t t t t t t t t




Prone to oxidation
t t




Negatively-charged (Acidic) Amino Acids -- Correct Answer ✔✔ Aspartic acid t t t t t t t t t t




(aspartate), glutamic acid (glutamate) t t t




Aspartic Acid (Aspartate) -- Correct Answer ✔✔ Carboxylate (-COO(-)) group in side
t t t t t t t t t t t t




chain
Deprotonated form of asparagine t t t




Glutamic Acid (Glutamate) -- Correct Answer ✔✔ Carboxylate (-COO(-)) group in side
t t t t t t t t t t t t




chain
Deprotonated form of glutamine t t t




Positively-charged (Basic) Amino Acids -- Correct Answer ✔✔ Lysine, arginine, histidine t t t t t t t t t t




Lysine -- Correct Answer ✔✔ Terminal primary amino group
t t t t t t t t

, Arginine -- Correct Answer ✔✔ Has 3 N atoms in side chain
t t t t t t t t t t t




Charge delocalized over all three N atoms
t t t t t t




Histidine -- Correct Answer ✔✔ Has aromatic ring with 2 N atoms (ring is called an
t t t t t t t t t t t t t t t t




imidazole)
At pH 7.4, one N is protonated and the other isn't
t t t t t t t t t t




Under acidic conditions, the 2nd N becomes protonated, making it positively charged
t t t t t t t t t t t




Hydrophobic Amino Acids -- Correct Answer ✔✔ Being repelled by water t t t t t t t t t t




Alanine, isoleucine, leucine, valine, phenylalanine
t t t t




More likely to be found in center of protein
t t t t t t t t




Nonpolar, uncharged compounds t t




Long alkyl chains
t t




Hydrophilic Amino Acids -- Correct Answer ✔✔ Being attracted to water t t t t t t t t t t




Histidine, arginine, lysine, glutamate, aspartate, asparagine, glutamine
t t t t t t




Polar and charged compounds and those that participate in H-bonding
t t t t t t t t t




Neither Really Hydrophobic/-philic -- Correct Answer ✔✔ Cysteine, threonine, serine,
t t t t t t t t t t




tyrosine, tryptophan, proline, methionine, glycinet t t t




Amphoteric -- Correct Answer ✔✔ Ability to act as an acid or a base t t t t t t t t t t t t t




Can either accept or donate a proton
t t t t t t




For ionizable groups: tend to be protonated at low pH; deprotonated at high pH
t t t t t t t t t t t t t




pKa -- Correct Answer ✔✔ The pH at which half of the species are deprotonated
t t t t t t t t t t t t t t




[HA] = [A(-)] t t




pKa1 -- Correct Answer ✔✔ pKa for carboxyl group
t t t t t t t t




Usually around 2 t t




pKa2 -- Correct Answer ✔✔ pKa for amino group
t t t t t t t t




Usually between 9 and 10 t t t t




pKa3 -- Correct Answer ✔✔ For amino acids with ionizable side chains
t t t t t t t t t t t